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AC Schnitzer kit

I have replaced the car's suspension with the AC.S kit, it runs about $2100 and is well worth the investment. It totally cures the car's pushy front end in fast tight corners, a problem that has nearly launched me off the Angeles Crest Highway twice!

Since replacing the suspension the car's manners have been a predictable delight, both on the street and on the track. It has totally eliminated all the push and plow tendencies of the standard set up, and the car now feels like it's on rails. The kit lowers the car some 25mm, and that also gives the car a very pleasing stance, as you can see of my shots at Willow Springs in the Gallery section.

The kit is imported into the States by CEC Wheels in West LA, and Albert Cook is the guy I dealt with there. The phone no is 310 203 3900.

Andrew Macpherson

Expert Z8 Inspections, with full support for both Z8 sale and purchases.

ACS ride quality

The roads in SoCal are basically superb, so the ACS kit has not had anything that it mightn't like thrown at it. I only use the car for long open road runs, and track days, so it has fairly ideal surfaces to deal with, but on those trips the ride quality seems excellent.
To be honest it is the handling that is always more the focus of my attention than the ride, and it is here that I have really noticed the improvement. I have certainly never been uncomfortable in the car since fitting the kit. I do tend to drive briskly, and so I like the car to 'feel' the road, and be as intouch with what is happeneing as possible, and that it does much better with the kit. You do feel more, whether that makes you uncomfortable or not is a personal thing, but I'm very happy with the way the car feels and handles.
Hope that helps!

Andrew Macpherson

Expert Z8 Inspections, with full support for both Z8 sale and purchases.

I changed to the ACS suspension first, brfore I upgraded tires and wheels. With the run flats the ride was substantially harder. Some might consider it bordering on the level of uncomfortably so. I didn't care too much since the handling improved dramatically. My biggest problem were wide fast turns on not perfect roads. The car felt bouncy and started swaying.

After I had the run flats replaced the ride feels perfect. Better grip, no diving or swaying and less harsh than with the run falts. I am running Bridgestone SO3s on HRE 19' 540 rims.

Review of the ACS Kit from Grease Monkey

The kit consists of replacement struts/shocks and springs. Eibach makes the springs to Schnitzer's specs and Sachs (maker of the original equipment units on the Z8) makes the new struts/shocks. The kit lowers the ride height of the Z8 by 30mm (1 3/16") front and rear and the stiffness is increased by 20-25%. I purchased the kit from CEC (the importer) in California (310-203-3900) for $1944 plus shipping. The list price is $2160 but BMWCCA members get the discounted price.

With the new suspension installed, the Z8 is visibly lower to the ground and looks more aggressive. The wheels/tires now fill up the wheel wells visually, lending the car a more modern appearance, less retro. As a result, the stock 18" wheels look more like 19-20" wheels would on an unmodified car. I think the proportions are just right.

I found the stock suspension set-up on the Z8 to be an almost perfect compromise between ride comfort and performance handling. The AC Schnitzer suspension shifts that balance substantially towards performance handling. The steering response and precision has gone from finely honed to razor sharp. Body lean while cornering has been noticeably reduced. Side to side maneuvers have virtually no lag in response, making the car feel extremely stable. Tire grip during hard street cornering has been enhanced to the point where it is difficult to break them loose. Best of all, the overall balance of the Z8's handling is even closer to neutral than before. These improvements are due to the lowered center of gravity, the increase in the spring stiffness and corresponding shock damping, and the more aggressive camber settings. All in all, the modified Z8 feels like it went on a diet and is down to fighting trim. I think exhilarating is the best way to describe the new driving experience.

Unfortunately, there is a price to pay for these improvements and that is in the ride comfort department. On freeways and relatively smooth roads, the difference is minimal and not at all bothersome. On rough pavement and when encountering substantial bumps, the ride is noticeably harsher, with a significant increase in vibration transmitted to your posterior. Fortunately, on all but the roughest roads, the stiffer suspension doesn't seem to interfere with the tires' ability to remain in contact with the pavement, so stability loss isn't a factor. However, I would now have to think twice before setting off on a long trip where a variety of road surfaces would be encountered. The car doesn't beat you up like some of the other exotics do, but the reduced ride comfort could prove fatiguing over a long period of driving. More than anything else, I have gained a new respect for the compromise chosen by the BMW engineers where handling and ride comfort are beautifully blended.

Having said that, I am not going back to the old set-up. The new-found handling precision and responsiveness are absolutely intoxicating and I'm not willing to give them up. Instead, I intend to experiment with tires to find a better overall balance. Currently, I'm using the Bridgestone RE040 run-flats that came with the car and while they have proven to be very responsive (extra-stiff sidewalls, no doubt) they are very hard riding. I believe I can improve upon their handling capabilities by switching to an ultra-high performance tire and hope to gain some ride comfort back through increased compliance. When the new version of the Michelin Pilot Sports is available, I will probably give them a try since they worked very well on the Z8s at the DE and I believe they were also used for much of the early Z8 testing since I have seen pictures of the test mules shod with the Michelins. Because I live in a very rural setting, a flat tire is a major concern and the new ZP (Zero Pressure) Pilot Sports may be an even better choice, assuming they make them in an appropriate size for the Z8.

The kit was relatively straight forward to install, taking less than a day. There are a few tools you must have (spring compressor, torque wrench, ball joint remover), but these are readily available. Any competent dealership or mechanic could certainly do the job for you. The springs were painted a beige color so I had them stripped and powder-coated in black to match the stock springs. The struts are visually identical to the originals. Nothing has to be modified during installation so you can easily return to stock configuration. The alignment of the steering (toe-in/out) does not change so once the new parts are installed, you're ready to roll. The camber settings of the front and rear wheels do change as a result of the lowered suspension, but the change increases the negative camber which just enhances the grip of the tires during hard cornering. You may experience an increase in tread wear as a result. Unfortunately, the camber settings are not adjustable on the Z8 so you will have to live with it.

If performance driving is your primary concern, I would not hesitate to recommend the Schnitzer suspension. The improvement is really dramatic! If you aren't willing to give up the ride qualities you now enjoy in your Z8, I'd keep it stock since you already have a world-class set-up.

Grease Monkey

Andrew Macpherson

Expert Z8 Inspections, with full support for both Z8 sale and purchases.

Andrew,
Nice write-up. I guess I didn't use so many words. I guess we came to the same conclusions. Still, I am certain you will like the ride even more with different tires. As I mentioned the ride was a little harsh for my taste with the runflats. The SO3s made all the difference. I have been in two over 1000 mile road trips (most of the time staying away from the interstates) and never felt fatigued. I was a little worried about getting to far away from civilisation. I really don't want to mess with any of that sticky stuff...

I was on a rally this past weekend, hitting many mountain roads. Twisting and cornering at "spirited" speeds, and I also almost lost the car form the inherent nose plow. I think I'm ready to do this mod, but I still have a question. If the ACS suspension is only made up of springs and shocks, how does one adjust the camber? GreaseMonkey made mention of this and I still don't understand how it works. I had a Dinan STG III suspension on my M5, it came with springs, shocks, rear strut bar and camber plates. The transformation was incredible.

Camber change

Hi Lupo,

I had the kit fitted by the importer, as they are just a couple of miles down the road from me, so I'm not sure how they set the camber. I would recommend calling Albert Cook at CEC Wheels, 310 203 3900, and asking him all the relevant questions.

Just as you were amazed by the transformation to the M5 I think you'll be thrilled with this too. I have now done 7 track days, as well as lots of spirited mountain road drives, and had no handling horrors of any kind.

Happy motoring!

Andrew Macpherson

Expert Z8 Inspections, with full support for both Z8 sale and purchases.

A fellow Z8 owner I talked to just ordered the Hamann coil over kit for his car. This set up will allow you to change settings to your liking. I believe the ACS kit is not adjustable but spring and shock come in perfect harmony. I like the ride a lot but you can't stiffen or soften it if you don't. Hamann is more expensive but it might be worth considering.

Re: Camber and AC Schnitzer Suspension

Camber is not adjustable on the Z8. However, when you install the AC Schnitzer suspension kit, the new springs lower the ride height of the car by app. 30mm and this lowering results in an increase in the negative camber settings on the front and the rear. Front goes from 1/2 degree (stock) to 1 degree and the rear goes from 1 1/2 degrees (stock) to 2 degrees. These increases are not unique to the Schnitzer kit; any lowering of the ride height will automatically increase negative camber.

Can you get anymore information on the Hamann coil over suspension. Is it adjustable from the cabin as with the ACS system for the M5? How does it ride?

I've had my Master Tech look into this for me, he wrote:

So far I have heard everything from "go with the hamann coil overs and have it corner balanced with the customer in it. " which is basically height adjustable coilovers with you and your car sitting on 4 scales and adjusting it to be equal weight at all corners or use the acs system and the lowering will increase the negative camber.

The Hamann system sounds very complicated, yet I'm worried about the ride on ACS... still can't make up my mind...

No, it is a thing of the past....

and as can be seen by the dates on all these posts they were made before the issues of the front shock towers doming came to light. I would advise that anyone with this system trade it back to stock, add the PP and run Michelin Pilot Sport 2 or similar non-runflat tires.

Andrew Macpherson

Expert Z8 Inspections, with full support for both Z8 sale and purchases.